Another chainsaw dyno...

[Red97]

You do any more hybrid runs yet Joe?

Not yet, prolly monday/Tuesday. Then I can make a day of running saws.

 

[Red97]

@Red97
Any stock or ported saws you want to see? I can try and get a couple started up before Sunday

That would be up to you, and these fellas.

I'm up for testing whatever you wanna send.

 

[ayoungtexan]

I can’t send it, as I don’t own one, but aany chance you could do a stock and a ported 421 or 4300

 

[Sawrain]

We shall see.

Project ultra light coming down the pipe.
View attachment 247541

Maybe a different feel, but I don't expect much if any gains in power. Going to test it on a 100% stock saw first. Then moved to modified.

Nice, interested.

I think we were (and it was fair enough) being called out for only talking of flywheel and crank weight, with no discussion on conrod and piston.

 

[huskyboy]

Nice, interested.

I think we were (and it was fair enough) being called out for only talking of flywheel and crank weight, with no discussion on conrod and piston.

I’ve always wondered how does rod length play into things? Two saws with the same stroke but one with a longer rod... It should affect dwell time between ports opening and closing right? Does it affect torque or rpm? This is where it starts to get a bit complicated....

 

[jacob j.]

@Red97
Any stock or ported saws you want to see? I can try and get a couple started up before Sunday

Joe told me in confidence that he's anxious to get a Roper 3.7 on the dyno, so that'd be great if you could help make that happen.

 

[huskyboy]

Some excerpts from https://www.enginebuildermag.com/2016/08/understanding-rod-ratios/ ..... What about longer rod ratios? Using longer connecting rods with the same stroke reduces the side loading on the pistons, which reduces friction. It also increases the piston dwell time at Top Dead Center. Holding compression for maybe half a degree of crankshaft rotation longer at TDC improves combustion efficiency and squeezes a little more power out of the air / fuel mixture. Typically, an engine with a higher rod ratio will produce a little more power from mid-range to peak RPM....... On the other hand, lower rod ratios do have some advantages. Shorter rods mean the overall height of the block can be shorter, which means the overall weight of the block can be lighter. The engine will typically pull more vacuum at low RPM, which means better throttle response and low end torque (good for street performance and everyday driving). Spark timing can be advanced a few degrees for some additional low speed torque, and the engine is less prone to detonation, which can be a plus in turbocharged, supercharged or nitrous applications.

 

[Red97]

Joe told me in confidence that he's anxious to get a Roper 3.7 on the dyno, so that'd be great if you could help make that happen.

Sxlao

 

[huskihl]

Joe told me in confidence that he's anxious to get a Roper 3.7 on the dyno, so that'd be great if you could help make that happen.

Just gotta send it

 

[ranchdadmike]

Maybe a bunch of folks ought to go on CL or OfferUp and find a nice ‘second string’ saw to send for testing, just to make dyno Joe’s day...

Might not create a Vegas betting pool...but maybe something in Biloxi

 

[Bigmac]

I’ve always wondered how does rod length play into things? Two saws with the same stroke but one with a longer rod... It should affect dwell time between ports opening and closing right? Does it affect torque or rpm? This is where it starts to get a bit complicated....

Have played with it in Trx250r’s a cr500’s and they are 2 different applications. So there are a bunch of variables to your question in a two stroke, When you increase the lot rod length do you space the cylinder base to compensate for the longer rod or do you move the piston pin via a different piston to create the same deck? In the TRX 250 R they changed the rod length 5 mm, and moved the piston pin up to have the same deck, the rod length effects port timing, shorter rod gives you more duration out of the same port heights, the shorter rod also seems to deliver a little more Violent power delivery, long rod is smoother, in the Honda it is popular to use the short rod piston with a long rod and spacer plate, more case volume Is good for big bores, more case volume can also be an advantage with a good pipe. On the cr500 the short rod has a short case and the long rod has a tall case, the short rod is extremely violent power, again it’s due to less case volume and port timing opening more aggressively because of the rod, the short rod feel like it has more power but the long rod dose make more peak power, but the feel of power, and ever one who ever rides a short rod 500 will tell you it has way more power, and it dose have more mid but peak power is still better with the long rod, but there are still a lot of variables and different ways to set it up!

 

[Red97]

Maybe a bunch of folks ought to go on CL or OfferUp and find a nice ‘second string’ saw to send for testing, just to make dyno Joe’s day...

Might not create a Vegas betting pool...but maybe something in Biloxi

Think so eh?

Pretty sure my mail lady already dosent like me

 

[huskihl]

Lol.
THE SLICER

 

[Nutball]

I wouldn't want a chainsaw called Heavy Hog, but I hear others do.

 

[Red97]

I can’t send it, as I don’t own one, but aany chance you could do a stock and a ported 421 or 4300

Me either. Have to look and see who has some built that would like to send in.

I can help a little on the first model tests.

But if it has already been on the dyno it is 50$ for a run/graph + return ship.

Have quite a few "targets " now for most any saw cc size. Easy to see where a particular saw falls in line now.

Very appreciative of those who have sent in saws, and continue to do so. Lots can be learned if we stay civil and ask the right questions.

 

[ranchdadmike]

Think so eh?

Pretty sure my mail lady already dosent like me

Since we’re talking off brand saws, we could use DHL for shipping. Save the USPS for the varsity

 

[huskihl]

I wouldn't want a chainsaw called Heavy Hog, but I hear others do.

I agree, although I do have a 166.


You should opt for..THE SLICER

 

[huskihl]

Since we’re talking off brand saws, we could use DHL for shipping. Save the USPS for the varsity

DHL must be busy also. They were supposed to pick up a 9010 3 weeks ago and ship it to England. They aren’t building a solid rep right now with me

 

[rogue60]

The only problem I can see is as soon as the chain touches the wood thasf extra energy would dissipate. Seems the engine would have to work harder to gain rpm again.

Maybe why most race saws have lighter flywheel vs a heavier one?

Spool back up just before returning back to the wood for the up cut?

When I first got a 661 I didn't like how it bogged so easy in the hardwood I was cutting that was just with a 25in bar and 404.
Was touchy as had to feather it in wood I found changing the clutch shoes to heavier older 660 shoes made a big difference.
The throttle response was slower but it only made it like a 660 and it don't bog so easy would just keep pulling the chain didn't have to baby it like before.
Doesn't take much weight to make a big difference it seems.
I used the 660 spring's as well they are weaker and keep the clutch shoes engaged at lower rpm than 661 spring's.

 

[Terry Syd]

Interesting, I considered the term 'bogging' as when the engine quickly falls off the torque curve, the revs drop and the centrifugal clutch slips. You can often fix that problem with a richer jetting in the low speed circuit to increase the low speed torque to keep the revs up.

In your definition, it was a clutch that slipped at lower revs. In other words, you could keep leaning on it, the engine had the torque, but the clutch would begin to slip.

EDIT: I wonder if the later clutch with the lighter shoes and stronger springs was an EPA idea. That is, it made the user keep the revs up so there was less emissions out the exhaust port at very low revs.